Low carbohydrate, higher-fat diets – such as the Atkins, Zone and South Beach – may not cause harm to arteries in obese people seeking to lose weight, compared to low-fat diets, according to two new Johns Hopkins studies. And low-carb diets may lead to more rapid weight loss. Researchers at Hopkins Heart and Vascular Institute conducted what may be the first comparison of such diets on vascular health. They researched the potential negative effects of the low-carb diets’ higher fat content.

Twenty-three men and women weighing an average of 218 pounds spent six months on a weight -loss program of moderate exercise and a diet that included up to 30% of calories from carbohydrates and 40% from dietary fats from meat, dairy products and nuts. Study subjects ranged from 30-65, and other than being overweight or obese, were considered to be in good health.

A second group of 23 dieters also undertook moderate exercise, but were placed on a low-fat, higher-carbohydrate diet, consisting of no more than 30% of calories from fat, 55% from carbs and the remaining 15% or more from protein.

There were no differences in vascular health between the groups following 10 pounds of weight loss. In each group, vascular health was determined by two key measures, including vascular relaxation after stressing the vessels and arterial stiffness as one might find in vascular disease. Moreover, low-carb dieters dropped on average 10 pounds after 45 days, whereas the low-fat group required, on average, 70 days to lose the same amount of weight.

An interesting side note: Before the weight-loss trial, researchers examined the short-term effect on vascular health following consumption of an extremely high-fat McDonald’s breakfast meal. This jumbo 900-calorie breakfast with 50 grams of fat had no immediate, harmful effect on the vessels. In fact, the vessels of study participants were actually less stiff and the linings functioned normally when tested four hours after consuming two McMuffins – one with egg and one with sausage – along with hash browns and decaf coffee. (Keep in mind these were overweight, but otherwise healthy people without high blood pressure, and they were not affected by the high-salt load of such a meal.

These results add to the growing body of positive reports on the safety and health benefits of low-carb, higher-fat content diets.

Just last year, researchers at Temple University's Center for Obesity Research and Education found that low-carb diets produced a two-fold gain in so-called good cholesterol levels compared to low-fat diets, despite roughly equal weight loss, over a two-year period.

Low-carbohydrate diets also are reported to be more effective than low-fat diets for insulin-resistant women, resulting in more weight loss after three months, compared to a low-fat diet with the same number of calories. People with insulin resistance are typically overweight and often progress to type 2 diabetes. They process carbohydrates less effectively and, therefore, a low-carb diet would be expected to be better tolerated than a higher carbohydrate diet.